1. Field of Invention
This invention relates to an integrated circuit formed by a semiconductor; and more particularly, to an integrated circuit wherein errors due to variations in resistance values of semiconductor resistances, such as polysilicon resistors and diffused resistors, are suppressed.
2. Description of the Prior Art
It was once though that the resistance value of a polysilicon resistor, which is an integrated circuit formed of a semiconductor, does not depend on the applied electric field,or other factor; and, thus is suited for an accurate electric circuit. However, as pointed out by Y. Akazawa and A. Iwata in "Recent Trends in High performance A-D and D-A conversion LSI", NTT R & D, Vol. 39, Nov. 1, 1990, pp 55-64, resistance value varies depending on the inter-electrode voltage. The effect of the resistance variation can be reduced by reducing the voltage applied per unit length of the resistor. In a circuit whose characteristics are determined by the ratio of one resistance part to the remaining resistance part, such as an attenuator, resistance variations produce no effects and so no great problem occurs.
However, the inventors hereof have experimentally discovered that the resistance value changes according to the potential difference with the substrate. This is an impediment to realization of an accurate electric circuit.